1. Field of the Invention
The invention relates to an optical lens.
2. Description of Related Art
Optical lenses are key components in various optical systems, and usually determine the optical quality of the optical systems. An optical lens may be a projection lens which projects an image from an image source, for example, a light valve or a display, onto a screen or a lens forming a virtual image of an image source in a virtual image display. Alternatively, an optical lens may be an image-forming lens which forms a real image of an external subject onto an image sensor inside a camera.
Generally, a longer projection distance is required if a projector needs to projects an image onto a larger screen. Contrarily, a special wide-angle lens is usually required if the image needs to be projected onto the larger screen from a shorter projection distance. However, a wide viewing angle and a large aperture may cause aberration. How to reduce image aberration is one of the major subjects in the design of wide-angle lenses.